A modulator such as a ΔΣ modulator is used in an audio device and an A/D converter. For example, the ΔΣ modulator quantizes an analog input signal into a one-bit quantized signal. Otherwise, the ΔΣ modulator may quantize an analog input signal into a quantized signal having a plurality of bits. A general ΔΣ modulator includes an adder (adder/subtractor), an integrator, a comparator, and a D/A converter (see, for example, Japanese Laid-open Patent Publication No. 2009-540716).
The adder subtracts a feedback signal from the analog input signal. The integrator integrates the output of the adder. Then, the comparator compares the output of the integrator with a reference value. Based on the comparison result, a quantized signal is generated. Further, the D/A converter performs D/A conversion on the output of the comparator (quantized signal) to generates a feedback signal.
A signal-to-noise ratio (hereinafter may be simplified as an “SNR”), may be improved by, for example, increasing a sampling frequency. Otherwise, the SNR may also be improved by increasing the number of bits of the output signal of the modulator. Further, in the general ΔΣ modulator generating a quantized signal having a plurality of bits, the comparator includes an A/D converter generating (outputting) a plurality of bits.
Reference may be made to Japanese Laid-open Patent Publication No. 2009-540716.